Page 86 - Pipeline Pigging Technology

Pigging for flexible pipes

PIGGING AND INSPECTION

OF FLEXIBLE PIPES

INTRODUCTION

The current proliferation in the use of flexible pipes from the drill floor to
the seabed largely derives from early successes achieved in the late 1970s in
the application of flowlines and static risers. At that time, there was an
industry demand to develop an alternative pipeline construction to that of
rigid pipe, which could be quickly laid using more economical installation
vessels and which could offer greater tolerance for misalignments. Early-
product developments utilized a composite of steel and polymer materials to
construct a layered structure which could offer greater chemical resistance
and structural flexibility than that offered by steel pipe. Technical develop-
ment progressed along two paths - that based on making submarine power
cables; and that based on the making of steel-reinforced hoses.
Today these two manufacturing technologies offer the oil industry alterna-
tive product constructions known as the bonded and non-bonded type
flexible pipes. By utilizing the inherent chemical resistances and mechanical
properties of its component parts, flexible pipe offers a composite construc-
tion having the advantages of: a low bending radius; good thermal character-
istics; high dampening coefficient; and high impact resistance. These and
other favourable properties related to stress distribution have prepared both
types of flexible pipe for use in increasingly more-demanding applications. In
fact, since 1979, more than 1600km (lOOOmiles) of flexible pipe has been
installed using both constructions.
As a result of successful operational experience with quasi-static risers and
dynamic topside jumpers in the past 15 years, pipe developments extended
this technology into the field of dynamic catenary risers. The need for such
risers began in Brazil in the early 1980s due to Petrobras' commitment to bring
oilfields onstream quickly using subsea and floating production systems. As an
alternative to using rigid risers having articulated or swivel joints, flexible
risers have been installed to connect fixed seabed hardware to floating units.

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